EP2188928B1 - Method and device for measuring the antenna diversity gain in digital radio transmission systems - Google Patents

Abstract

The invention relates to a method and a device for measuring the antenna diversity gain in digital radio transmission systems, wherein the sensitivity of a receiver system is designed by using a plurality of antennas, wherein the signals thereof determine a diversity gain (DG) by means of the bit error rate (BER)-increase of the signals. The invention is characterized in that the method and the device for measuring the diversity-gain (DG) in digital radio transmission systems form an optimization of radio net planning by means of targeted use of diversity, wherein a decrease of the number of used base stations and an increase of the transmission- and receiving quality is achieved.

Description

The invention relates to a method and a device for measuring the antenna diversity gain in digital radio transmission systems according to the preamble of claim 1.

Generally, the diversity gain is defined as the increase in receiver sensitivity over reception without diversity in a given propagation scenario.

An improvement in the sensitivity of a receiving system by using multiple antennas (generally two) is already known in radio systems in analog and digital technology.
In conventional mobile radio applications, antenna diversity arrangements are preferably used in order to reduce fading effects (fluctuations in the reception field strength in the case of radio transmissions).
However, a precisely defined and exactly quantifiable determination of the diversity gain (DG) has not been satisfactorily resolved in order to derive and optimize further system parameters, such as the required transmission power of a station for the planning.

According to the state of the art, the diversity gain (DG) is given statically (for a permanently defined link) with a defined antenna configuration.
This information is not sufficient for many applications, such as in mobile communications.
Therefore, a precise definition of the diversity gain (DG) is required. A proposal for determining diversity gain (DG) in portable terminals (teminals) is disclosed in the publication by Tsunekawa (Spatial, Polarization, and Pattern Diversity for Wireless Handheld Terminals).

Here, the diversity gain (DG) is determined by the S / N enhancement and the correlation factor of the signals supplied by two antennas.
The measurement of both values is extremely problematic, tedious and inaccurate (compare measurement to theory see Tsukenawa Figure 8 -4 (d)).

DE 197 27 516 A1 discloses a method of determining the internal noise of digital circuits using the relationship log (BER) = f (Pe) with C / I as a parameter also used in the method described below. In this case, parallel lines are also calculated by interpolation of adjacent straight lines.

US 5,812,539 A and US 2004/104844 A1 disclose (diversity) receiving systems and the use of interpolated / extrapolated values, whereby the input power at the receiving system is reduced, thereby producing a diversity gain.

The object of the present invention is thus seen to provide a method which provides a defined diversity gain (DG) value for a given radio transmission system (eg UMTS, B3G, WLAN) quickly and with high accuracy for development and planning ,

The solution of the problem is characterized by the features of claim 1.

An important feature is that the method and apparatus for measuring the diversity gain (DG) in digital radio transmission systems forms an optimization of radio network planning by means of a targeted use of diversity, whereby a reduction in the number of base stations used and an increase in the transmission and reception quality is formed is.

Thus, there is disclosed a method and apparatus for accurately and rapidly measuring the diversity gain (DG) of antenna arrays in digital, stationary and mobile radio communication systems.

An essential advantage of the method used is that the use of diversity and its exact quantification optimizes the radio network planning.

A further advantage is that the transmission quality is improved and / or the number of base stations in mobile radio systems is reduced.

The measurement of a diversity gain (DG) value with high accuracy by the method according to the invention is particularly important for future mobile radio systems (Beyond 3G), e.g. according to MIMO (Multiple Input Multiple Output) methods, in which the transmission paths should be as uncorrelated as possible, to optimize their transmission capacity.

For the intended course of the measurements, a measuring device will be described.

The measurements according to the invention can be carried out in operation on established base stations or in the laboratory, for example with the simulation of different propagation paths through a radio channel simulator.

From the measurement of the bit error rate (BER) and the receiver input power (P _Rx ) of a digital communication _transmission system, the diversity gain (DG) is determined in a given wave propagation scenario.

Since the bit error rate (BER) and the receiver input power (P _Rx ) can be measured very accurately, the diversity gain (DG) can also be determined with high accuracy by the method according to the invention.

In the following the invention will be explained in more detail with reference to illustrative drawings. Here are from the drawings and their description further features essential to the invention and advantages of the invention.

Figur 1:

Flussdiagramm des Verfahrens

Figur 2:

Darstellung Messung 1 (ohne Diversity)

Figur 3:

Darstellung Messung 2 (mit Diversity)

Figur 4:

graphische Darstellung der linearen Interpolation oder Extrapolation der Messwerte

Figur 5:

graphische Darstellung einer Diversity-Gewinn-Messung, z.B. an einer UMTS-Basisstation

Figur 6:

graphische Darstellung einer Funkstrecke mit einem Funkkanalsimulator ohne Diversity (n Übertragungswege)

Figur 7:

graphische Darstellung nach Figur 6 mit Diversity (2n Übertragungswege)

Figur 8:

graphische Darstellung der linearen Interpolation oder Extrapolation der Messwerte (Ausführungsbeispiel)

It shows:

FIG. 1:

Flowchart of the process

FIG. 2:

Presentation of measurement 1 (without diversity)

FIG. 3:

Presentation of measurement 2 (with diversity)

FIG. 4:

graphical representation of the linear interpolation or extrapolation of the measured values

FIG. 5:

graphical representation of a diversity gain measurement, for example on a UMTS base station

FIG. 6:

graphical representation of a radio link with a radio channel simulator without diversity (n transmission paths)

FIG. 7:

graphic representation after FIG. 6 with diversity (2n transmission paths)

FIG. 8:

graphical representation of the linear interpolation or extrapolation of the measured values (exemplary embodiment)

That in the FIGS. 1 to 8 illustrated method for measuring a diversity gain (DG) of a radio transmission system is shown by way of example for further embodiments for a measurement setup with a transmitting and two receiving antennas.

Analogous conditions arise with two transmitting and one receiving antenna (2, 4) (transmit diversity).

The measuring method is also suitable for more than two transmitting and / or receiving antennas, such as for MIMO systems.

• Typ und Konfiguration der Antennen
• Frequenz
• Ausbreitungsszenario
• Diversity-Algorithmus des Empfängers.

The diversity gain depends on the following factors:

• Type and configuration of the antennas
• frequency
• spread scenario
• Diversity algorithm of the receiver.

Since different propagation scenarios and hence diversity gains can occur in mobile radio, limits (minimum and maximum diversity gain) or averaging of the diversity gain are proposed.

A radio transmission system can be planned with a "best case", "worst case" or a weighted average of the diversity gain.

• konstante Leistung P_Tx, eines Senders (1) an einer Antenne (3) (Fig.2 und Fig.3)
• quasi-stationäre Ausbreitungsbedingungen
  (invariante Ausbreitungswege und gleiches Fading)
• konstante Geschwindigkeit einer Station in Mobilfunksystemen.

The method for measuring the diversity gain (DG) is performed under the following conditions during a measurement:

• constant power P _Tx , of a transmitter (1) on an antenna (3) ( Fig.2 and Figure 3 )
• quasi-stationary propagation conditions
  (invariant propagation paths and the same fading)
• constant speed of a station in mobile radio systems.

1. 1. Messung der Leistung der Einhüllenden (envelope power) der Eingangsleistung P_Rx(1) des Empfängers 4 mit einer Empfangsantenne 3 und der korrespondierenden Bitfehlerrate (BER[1]).
2. 2. Einstellung der Eingangsleistung P_Rx(1) an den Diversityeingängen des Empfängers 4 mit den Empfangsantennen 5 und 6.
   Ein Dämpfungseinsteller 7 steht in beiden Zweigen auf 0 dB.
   Da durch den Empfang der möglichst unkorrelierten Signale der beiden
   Antennen 5, 6 eine Verbesserung der Übertragung stattfinden soll, wird eine Bitfehlerrate BER(1) > BER(2) erwartet.
3. 3. Reduzierung der Eingangsleistung in beiden Diversityzweigen gleichmäßig mit dem Dämpfungseinsteller 7, um den ungefähr zu erwarteten Diversity-Gewinn auf die Eingangsleistung P_Rx(3) so, dass die Bitfehlerrate BER[3] - BER[1] ist (siehe Fig. 4).
   Dies entspricht einer Reduzierung der Sendeleistung P_TX, um die mit dem Dämpfungseinsteller 7 eingestellte Dämpfung.
4. 4. Lineare Interpolation oder Extrapolation der Messwerte der Eingangsleistungen P_Rx(2) und P_Rx(3), um die Eingangsleistung(P_Rx* für die Bitfehlerrate BER(1) zu berechnen (Fig.4).

The FIGS. 1 to 8 show the measuring method, which is described in more detail in the following steps.

1. 1. Measuring the power of the envelope (envelope power) of the input power P _Rx (1) of the receiver 4 with a receiving antenna 3 and the corresponding bit error rate (BER [1]).
2. 2. Setting of the input power P _Rx (1) at the diversity inputs of the receiver 4 with the receiving antennas 5 and 6.
   A damping adjuster 7 is at 0 dB in both branches.
   Because by the receipt of the most uncorrelated signals of the two
   Antennas 5, 6 should take place to improve the transmission, a bit error rate BER (1)> BER (2) is expected.
3. 3. Reduction of the input power in both diversity branches evenly with the attenuation setter 7 to give the approximately expected diversity gain on the input power P _Rx (3) such that the bit error rate BER [3] - BER [1] (see Fig. 4 ).
   This corresponds to a reduction of the transmission power P _TX to the damping set with the damping adjuster 7.
4. 4. Linear interpolation or extrapolation of the measured values of the input _powers P _Rx (2) and P _Rx (3) in order to calculate the input power (P _Rx * for the bit error rate BER (1) ( Figure 4 ).

From the publication of Kamilo Feher " MODEMS for Emerging Digital Cellular Mobile Radio System ", IEEE Transactions on Vehicular Technology, May 1991 or off DE 197 27 516 B4 It is known that the logarithm of the bit error rate in the range of interest here is reciprocally linearly proportional to the input power.

Results:

• 5. Bestimmung des Diversity-Gewinns (DG):
  DG/db = P_Rx(1)/dBm - P_Rx*/dBm

Bit error rate BER (1) at input power P _Rx (1) without diversity and input power P _Rx * with diversity.

• 5. Determination of Diversity Profit (DG):
  DG / db = P _Rx (1) / dBm - P _Rx * / dBm

The measurements according to items 2 to 5 are independent of the algorithm with which the diversity signals in the receiver 4 are processed. Therefore, this measurement method can also compare the effectiveness of different diversity methods and MIMO systems.

Preferably, the propagation conditions are defined with the aim of better reproducibility of the measurements with a radio channel simulator 8.

An embodiment of the invention which is advantageous for mobile radio systems is a diversity gain (DG) determination of the base station antenna systems for connections which provide a high and a low diversity gain (DG) value in accordance with the propagation conditions in the radio cell (diversity gain limit values of Antenna system in a radio cell).

Preferably, the measurement processes are after FIG. 1 automatically performed.

A computer 9 controls and detects the measurements 1 to 3 according to Fig. 1 , then performs the interpolation and calculates the diversity gain (DG).

As an example, the diversity gain measurement on a UMTS base station with two diversity antenna inputs is explained. The radio link is formed with a radio channel simulator 8 with n transmission paths without diversity and 2n transmission paths with diversity ( Fig. 6 and 7 ).

Measurement 1 (FIG. 6):

Simulation of n (eg n = 4 to 3G TS 25.104) Transmission paths between the output of the transmitter 1 and the output of the radio channel simulator 8.
Measurement of the input power P _Rx (1) and the bit error rate BER (1) (eg P _Rx (1) = -112 dBm and BER (1) = 1.1 · 10 ^-6 ).

Measurement 2 (Figure 7):

Same setting of the radio channel simulator 8, as in measurement 1.
Additional reception via the second diversity channel with the same settings as channel 1.
Measurement of the input power P _Rx (2) and the bit error rate BER (2) (eg P _Rx (2) = -112 dBm and BER (2) = 0.6 · 10 ^-6 ).

Measurement 3 (Figure 7):

Reduction of the receiver input power P _Rx with the attenuation adjuster 7 by 4 dB (expected diversity gain): P _Rx (3) = -116 dBm and BER (3) = 10 ^-6 ).

Extrapolation (Figure 8):

With the exemplary measurement results, by extrapolating the two measurements 2 and 3, the bit error rate BER (1) = 1.1 × 10 ^-6 (measurement 1) results at P _Rx * = -116.7 dBm.

Diversity gain (DG) determination:

This results in:
Diversity gain = -112 dBm - (-116.7 dBm) = 4.7 dB.

The duration of a measurement process (measurements 1 to 3) via for example. 2 × 10 ⁶ bits is about 5 s for UMTS with a transmission rate of 384 kBit / s.

For propagation conditions with very slow fading, the measurement duration can be extended.
With automatic adjustment and evaluation of the three measured values, a diversity gain measurement can be carried out in <1 min.
As a result, variations for optimization measures on the planning concept and / or the antenna system can be carried out relatively quickly.

Through the targeted use of diversity, the radio network planning can be optimized, the quality improved and / or base stations saved.

With the method and the device according to claims 1 to 8, a meaningful, accurate and quickly performed method for optimizing base stations is provided.

The subject of the present invention results not only from the subject matter of the individual claims, but also from the combination of the individual claims with each other.

LIST OF REFERENCE NUMBERS

1.

transmitter

Second

transmitting antenna

Third

receiving antenna

4th

receiver

5th

Receiving antenna 1 (diversity)

6th

Receiving Antenna 2 (Diversity)

7th

Damping adjuster

8th.

Radio channel simulator

9th

computer

Claims (11)

1. Method for measuring the antenna diversity gain of digital systems by measuring the improvement in receiver system sensitivity by means of the bit error rate (BER), characterised in that the method has the following steps:

   - measurement of the input power P_RX(1) of the receiver system (4) and the corresponding bit error rate BER(1) for the respective propagation scenario with one antenna (3);

   - measurement of the bit error rate BER(2) at the receiver system (4) with the same system input power P_RX(2) = P_RX(1) with several antennas (5, 6);

   - reduction of the input power at the receiver system (4) to an input power P_RX(3) at which the associated bit error rate BER(3) is approximately equal to the bit error rate BER(1) as in step 1;

   - determination of an input power to be expected P_RX* at the bit error rate BER(3) from the measured input powers (P_RX(1), P_RX(2)) and the bit error rates BER(1), BER(2) and BER(3) by means of interpolation/ extrapolation;

   - determination of the diversity gain DG from the difference between the input powers P_RX(1) and P_RX*.
2. Method according to claim 1, characterised in that the method is designed for measurements in reciprocal transmitter-antenna diversity operation.
3. Method according to one of the preceding claims 1 to 2, characterised in that the measurements necessary for determining the diversity gain (DG) value can be carried out by means of base stations which are in operation or in the laboratory, wherein the DG values measured in the laboratory are measured with the simulation of different paths of propagation by means of a radio channel simulator (8).
4. Method according to one of the preceding claims 1 to 3, characterised in that the diversity gain (DG) value can be determined from a precisely measurable bit error rate and receiver input power.
5. Method according to one of the preceding claims 1 to 4, characterised in that the measurement method is carried out on a measuring structure with at least one transmitter antenna and at least two receiver antennas (5, 6).
6. Method according to one of the preceding claims 1 to 5, characterised in that the diversity gain (DG) is determined by the following factors:

   - type and configuration of antennas;

   - frequency;

   - propagation scenario;

   - diversity algorithm of the receiver.
7. Method according to one of the preceding claims 1 to 6, characterised in that the radio transmission system can be designed by means of an upper or lower limit value or by means of an average value of diversity gain (DG).
8. Method according to one of the preceding claims 1 to 7, characterised in that

   - a constant power of a transmitter (1) exists at an antenna (2);

   - quasi-stationary propagation conditions exist;

   - a constant speed of a station in mobile telephone systems exists.
9. Method according to one of the preceding claims 1 to 8, characterised in that the measurement has the following steps:

   - measurement of the input power of the receiver (4);

   - measurement of the corresponding bit error rate with at least one receiver antenna (5, 6);

   - attenuation of the signal by means of an attenuation adjuster (7);

   - reduction of the input power to a bit error rate BER(3) ~ BER(1);

   - linear interpolation or extrapolation of the measured values of input power of P_RX(1) and P_RX(2) and calculation of the input power to be expected P_RX* for calculation of the bit error rate;

   - determination of the diversity gain (DG).
10. Method according to one of the preceding claims 1 to 9, characterised in that an attenuation adjuster (7) is used for reduction of the input power at the receiver system (4).
11. Method according to one of the preceding claims 1 to 10, characterised in that it is carried out on a computer (9) which automatically performs, detects and interpolates the measurements and carries out calculation of the diversity gain (DG).

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